The present invention relates to support devices for semitrailers, and more particularly to a hydraulically-operated support device wherein the operations of extension, load raising and retraction are each carried out by separate units.
Support devices are used to lift semitrailers when they are uncoupled from or coupled to their tractor. Various constructions of support devices of this kind are known. When such devices are hydraulically operated, they are generally simple hydraulic cylinder arrangements pressurized by separately attached pump units which may have a variable transmission ratio, thus entailing complicated constructions and heavy stresses.